> I am replacing my 4200 series Slick Magnetos on my
> Lancair 320 powered by a Lycoming O-320-E2D engine.
> I need to remove the drive gear from the shaft of the
> magneto and transfer the drive gear to the new magnetos.
> I have successfully removed the cotter pin from the castle
> nut on the end of the shaft.  How do I remove the castle
> nut from the drive gear?  I need some means to hold the shaft
> of the magneto while I'm trying to break the castle nut free.
> Any suggestions?

Just clamp the gear between two boards in a vice.
That's what I saw Al Marcucci do at Savage Magneto.
Then loosen the castle nut with a socket wrench.
Before removing the nut, whack it with a plastic hammer to
break the gear free of the tapered shaft. Then remove the nut.

> Once I get the nut free and install the drive gear on the
> new magnetos, what is the tightening torque for the castle nut?

Sorry. I don't remember that torque.

I do remember that pre-curving the cotter pin is essential
to getting it back into the hole. Remember to use a non-plated
cotter pin.

> One final question, where can I purchase the Slick locating
> pin that aligns the magneto prior to installation in the engine?

I just use an allen wrench. But then I get I usually take three
tries to get it right :-) Here's a better way....

http://www.sacskyranch.com/faq_slick_magneto/FAQ00002.htm

Aviall has the T-118 Slick alignment pin for $3.21 (your price may vary).
Chief, Spruce, Aircraft Tool Supply etc probably also carry that tool.